Succession and Colonization Dynamics of Endolithic Phototrophs within Intertidal Carbonates

Abstract

Photosynthetic endolithic communities are common in shallow marine carbonates, contributing significantly to their bioerosion. Cyanobacteria are well known from these settings, where a few are euendoliths, actively boring into the virgin substrate. Recently, anoxygenic phototrophs were reported as significant inhabitants of endolithic communities, but it is unknown if they are euendoliths or simply colonize available pore spaces secondarily. To answer this and to establish the dynamics of colonization, nonporous travertine tiles were anchored onto intertidal beach rock in Isla de Mona, Puerto Rico, and developing endolithic communities were examined with time, both molecularly and with photopigment biomarkers. By 9 months, while cyanobacterial biomass and diversity reached levels indistinguishable from those of nearby climax communities, anoxygenic phototrophs remained marginal, suggesting that they are secondary colonizers. Early in the colonization, a novel group of cyanobacteria (unknown boring cluster, UBC) without cultivated representatives, emerged as the most common euendolith, but by 6 months, canonical euendoliths such as Plectonema (Leptolyngbya) sp., Mastigocoleus sp., and Pleurocapsalean clades displaced UBC in dominance. Later, the proportion of euendolithic cyanobacterial biomass decreased, as nonboring endoliths outcompeted pioneers within the already excavated substrate. Our findings demonstrate that endolithic cyanobacterial succession within hard carbonates is complex but can attain maturity within a year’s time.

The allometry of cellular DNA and ribosomal gene content among microbes and its use for the assessment of microbiome community structure

“…A procedural explanation is given under the “Methods” section, and we provide an example application in Fig. 2 using a dataset of phototrophic bacteria from endolithic microbiomes within intertidal hard carbonate rocks [ 22 ], responsible for their micritization and bioerosion [ 23 ], and useful here because typical cell volumes could be assigned to all taxa. The differential outcomes are obvious: 16S rRNA counts of large-celled cyanobacterial genera severely underestimate their contribution to biomass but overestimate their contribution in terms of number of cells (see for example, Hyella sp.).…”

“…1 . The dataset is from Roush et al [ 22 ] and includes the subset of taxonomically assignable phototrophic bacteria from an endolithic microbiome on coastal marine carbonate rocks. Only three exemplary phototrophs are labeled, but full, taxonomically explicit distributional data are in Table S3 (see Additional file 3 ).…”

The allometry of cellular DNA and ribosomal gene content among microbes and its use for the assessment of microbiome community structure

“…For three species, we plotted datasets to highlight intraspecies variability: Synechococcus elongatus (light blue symbols) (28), Colozoum pelagicum (light purple) (19), and Sphaerozoum fuscum (19) (light yellow). (22), and includes the subset of taxonomically assignable phototrophic bacteria from an endolithic microbiome on coastal marine carbonate rocks. Only three exemplary phototrophs are labeled, but full, taxonomically explicit distributional data are in Table S3 (see Additional file 3).…”

“…A procedural explanation is given under Methods, and we provide an example application in Fig. 2 using a dataset of phototrophic bacteria from endolithic microbiomes within intertidal hard carbonate rocks (22), responsible for their micritization and bioerosion (23), and useful here because typical cell volumes could be assigned to all taxa. The differential outcomes are S3 (see Additional file 3).…”

Editorial for the Special Issue: Advances in the Biology of Phototrophic Bacteria

“…This Special Issue highlights recent advances in these aspects. It includes results specifically on green sulfur bacteria (Chlorobi [3]), heliobacteria (Firmicutes [4]), Chloroflexi [5], Cyanobacteria [6,7] and phototrophic purple bacteria (Proteobacteria [8][9][10][11][12][13]). In addition, phylogenetic studies regarding photosynthesis and osmotic adaptation consider representatives of all of these phyla [14,15].…”